Chair back cushions are buffeted by every wind that blows, and periodic summer rains run from the top of the cushion down, creating a greater opportunity for taking on moisture through the seams, with the resulting risk of mold and mildew.
Numerous attempts have been made to find periodic variations in thunderstorm frequency.
"Time for our periodic chat, little brother," he said, and motioned to the other chair before the hearth.
In spite, however, of all that has been done, the Elbe remains subject to serious inundations at periodic intervals.
In its chemical relations, titanium is generally tetravalent, and occurs in the same sub-group of the periodic classification as zirconium, cerium and thorium.